The white van used to plough into Muslim worshippers near a mosque belonged to a hire firm in Wales.
Police officers were at the office of Pontyclun Van Hire within hours of the incident which occurred about 165 miles away in north London.
The van's driver was detained by worshippers outside the Muslim Welfare House, near Finsbury Park Mosque, until police arrived.
Met Police said the attack was being treated as a "terrorist incident" and the driver was arrested on suspicion of attempted murder.
Witnesses have described hearing the driver shout "I'm going to kill Muslims".
A woman who answered the phone at Pontyclun Van Hire's office, in an industrial estate in the village of Pontyclun, west of Cardiff, said the firm would not comment on the incident at this time.
The van, which featured the company's logos, phone number and website address, was searched by forensics officers.
The company's website states that it has been in business for more than 25 years.
The website states: "Established for over 25 years, Pontyclun Van Hire provide quality vans, trucks and other vehicles for hire in the South Wales area."
The firm also provides truck, minibus and car hires and self storage services.
Worshippers observing Ramadan were leaving evening prayers at the Muslim Welfare House in Seven Sisters Road when the pedestrians were hit.
A man died at the scene and eight people were taken to hospital.